Site Solution Preference of $\hbox {Bi}^{3+}$ in $\hbox {RE}_{2}\hbox {O}_{3}$ Scintillators

Atomic-scale simulations have been employed to predict the site solution preference of Bi³⁺ activator cations in a series of RE₂O₃ scintillators with the bixbyite crystal structure (Ialpha3), where RE denotes a 3+ cation ranging in size from Sc³⁺ to La³⁺ . There are two crystallographically unique cation sites in the bixbyite structure, in Wyckoff notation referred to as the 24d and 8b site. It is expected that the spectroscopic properties of an activator cation residing on the 24d site will be different from the same activator cation residing on the 8b site, due to the distinct symmetries (C₂ and S₆ respectively) of these two sites. Previous studies have revealed two different Bi³⁺ emissions in Y₂O₃ corresponding to Bi³⁺ cations occupying both lattice 24d and 8b sites. By predicting the energy difference of the Bi³⁺ solution on the 24d and 8b sites, we are able to predict the distribution of Bi³⁺ in a range of bixbyite compounds.